JPH1089048A - Exhaust fine particle purifying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate the trapping amount according to the operating state without using any map data. SOLUTION: A collection amount DPEMn is calculated (step 101) on the basis of filter differential pressure, the mean exhaust gas temperature X1 after filter regeneration, the mean intake amount X2, a value X3 obtained by dividing the total intake amount by the ventilation resistance increase amount, and a value X4 obtained by dividing the collection time by the ventilation resistance increase amount are found (steps 102 to 106), the correction coefficient is calculated (step 107) by using these values X1 to X4, the collection amount DOEMn found in the step 101 is multiplied by the correction coefficient X, and correction of the collection amount is performed (step 108). The collection amount having little variations in relation to the regeneration temperature can be obtained according to the operating state by performing such the correction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for purifying exhaust particulates which collects exhaust particulates contained in exhaust gas of a diesel engine using a filter and burns the collected exhaust particulates to regenerate the filter. .

[0002]

2. Description of the Related Art Since the exhaust gas of a diesel engine contains a large amount of exhaust particulates (hereinafter referred to as "particulates"), a filter for trapping the particulates is provided in an exhaust passage. When the amount of particulates accumulated inside the filter increases with use, the air permeability gradually deteriorates and the performance deteriorates. Therefore, when the trapping amount of the filter exceeds a predetermined amount, the filter is regenerated. .

[0003] The regeneration of the filter means that the particulates are burned and removed by operating a regeneration means such as an electric heater provided on the end face of the filter or an air pump for supplying air required for the combustion of the particulates. Means The amount of particulates collected by the filter described above can be determined from the differential pressure across the filter (filter differential pressure) because it corresponds to the ventilation resistance of the filter.

[0004]

However, even with the same trapping amount, depending on the composition of the particulates,
The regeneration temperature for regeneration is different. That is, the composition of particulates consists of dry soot mainly composed of carbon and soluble substances (SOF) composed of unburned fuel and engine oil. These two substances have significantly different heat values per unit weight. Depending on the composition of the curate, the regenerating temperature differs even with the same trapping amount. Therefore, it is necessary to estimate the trapping amount in consideration of the constituent components of the particulates.

The applicant of the present invention has noticed that the composition of the particulates varies depending on the operating state of the engine, and uses interpolation calculation of a two-dimensional map from the engine speed and the accelerator opening indicating the operating state of the engine. A component correction coefficient was calculated, and the trapping amount obtained from the filter differential pressure was estimated based on the component correction coefficient. An application was filed earlier (Japanese Patent Application Laid-Open No. 7-310524).

However, in order to prepare the above-described two-dimensional map, it is necessary to carry out an experiment for each engine to acquire the data of the map grid points, and most of the actual running is in a transient state. There is a problem that deviation from data occurs. The present invention has been made in view of the above problems, and has as its object to estimate a trapping amount according to a driving state without using map data.

[0007]

Means for Solving the Problems The present inventors have examined the relationship between the trapping amount obtained from the filter differential pressure and the filter regeneration temperature with respect to the trapping amount under various operating conditions. The 16 types of operating conditions shown in the lower table of FIG. 5 were set, and the trapping amount and the regeneration temperature obtained from the filter differential pressure were plotted under each operating condition. As shown in the graph, large variations occurred. This is because the particulate composition components differ depending on the respective operating conditions. Therefore, using the trapping amount obtained from the filter differential pressure as it is,
The filter cannot be regenerated at the right time,
Problems such as erosion and unburned filter may occur.

Therefore, the present inventors investigated various correlations between the trapping amount obtained from the filter differential pressure and the regeneration temperature using various variables in the operating state. The results are shown in FIGS. FIG. 6 shows a case where the collection amount is corrected by using the average exhaust temperature at the time of collection from the start of collection with the filter after regeneration to the present, and FIG. Fig. 8 shows the total amount of data collected from the start of collection by the filter whose regeneration has been completed to the present, when the collection amount was corrected using the average intake air amount of the diesel engine during collection from the start of the collection to the present. When the trapping amount is corrected using the value obtained by dividing the intake air amount by the ventilation resistance increase amount, FIG. 9 shows the collection time from the start of the collection by the filter whose regeneration has been completed to the present time to the ventilation resistance increase amount. 5 is a graph showing the relationship between the corrected trapping amount and the regeneration temperature when the trapping amount is corrected by using the value obtained by dividing by (1). In addition, the characteristic shown by the solid line rising to the right shows the relationship between the trapping amount obtained under specific reference operating conditions and the regeneration temperature. As can be seen from these results, by correcting the trapping amount using those variables, the variation in the regeneration temperature with respect to the corrected trapping amount was greatly reduced, and the characteristics could be made closer to the characteristics under the standard operating conditions.

Further, when the collection amount was corrected using all of the above variables, very good results were obtained as shown in FIG. The present invention has been made based on the above study. In the invention according to claim 1, an average value obtained by integrating the exhaust gas temperature at the time of collecting the filter after regeneration of the filter and dividing the integrated value by the number of times of integration. It is characterized in that the trapping amount is corrected based on the following.

According to the second aspect of the present invention, the amount of intake air at the time of filter collection after filter regeneration is integrated, and the amount of collection is corrected based on an average value obtained by dividing the integrated value by the number of times of integration. Features. The invention according to claim 3 is characterized in that the intake air amount at the time of collecting the filter after the regeneration of the filter is integrated, and the collected amount is corrected based on a value obtained by dividing the integrated value by the increase amount of the ventilation resistance. I have.

[0011] The invention according to claim 4 is characterized in that the trapping time is integrated after the regeneration of the filter, and the trapping amount is corrected based on a value obtained by dividing the integrated value by an increase in the ventilation resistance. . According to the first to fourth aspects of the present invention, it is possible to obtain a trapping amount with a small variation with respect to the regeneration temperature according to the operation state without using the map data unlike the conventional one.

Further, in the invention according to claim 5,
It is characterized in that the above-described integrated value is subtracted in accordance with the amount of reproduction when the filter is reproduced. As a result, even if the regeneration is interrupted halfway and ended in an incomplete regeneration, the deviation in the relationship between the particulate component accumulated in the filter and the integrated value when resuming the next collection is reduced. In addition, it is possible to accurately estimate the next collection amount.

[0013]

FIG. 1 shows a schematic configuration of an exhaust gas purifying apparatus for a diesel engine according to an embodiment of the present invention. Air cleaner 2 on the intake side of diesel engine 1
A hot-wire type flow sensor 3 for detecting the intake air amount is provided in the middle of the flow path from the air cleaner 2 to the diesel engine 1.

An exhaust purification device 5 is provided in an exhaust pipe 4 of the diesel engine 1. This exhaust gas purification device 5
A housing 6 connected to the exhaust pipe 4;
A filter 7 made of a porous ceramic is provided in the housing 6. When the exhaust gas passes through the filter 7, the particulates contained in the exhaust gas are collected.

On the diesel engine 1 side of the filter 7, a pressure sensor 11 for detecting the pressure on the upstream side of the filter 7 (pre-filter pressure) and a temperature sensor 13 for detecting the temperature of exhaust gas flowing from the diesel engine 1 into the filter 7 are provided. ing. Further, a pressure sensor 12 for detecting a pressure on the downstream side of the filter 7 (post-filter pressure) is provided on the exhaust side of the filter 7.

A heating device (electric heater) 8 for igniting the particulates collected by the filter 7 at the time of regeneration of the filter is provided on the filter 7, and secondary air for combustion at the time of regeneration of the combustion. An air pump (A / P) 9 and a valve 10 for supplying air are provided. The signal from each of the above sensors is sent to an electronic control unit (E
CU) 14. The ECU 14 estimates the amount of particulates collected by the filter 7 in order to prevent the filter 7 from being clogged. When the collected amount reaches a certain value, the ECU 14 activates the electric heater 8 to collect the particulates on the filter 7. Then, the particulates are ignited, the valve 10 is opened, and the secondary air for combustion is supplied from the air pump 9 to the filter 7, so that the filter 7 is controlled to burn and regenerate.

FIG. 2 shows a process for estimating the amount of trapped particulates performed by the ECU 14. First, based on signals from the hot-wire flow sensor 3, the pressure sensors 11, 12, and the temperature sensor 13, the filter differential pressure generated in the filter 7 is obtained by subtracting the post-filter pressure from the pre-filter pressure. The exhaust gas flow rate is obtained from the pressure and the exhaust temperature, and the filter differential pressure is standardized by the exhaust gas flow rate, and the trapping amount DPEM
n is calculated (step 101). The method of calculating the trapping amount is the same as the conventional one. In addition, the trapping amount in this case indicates the ventilation resistance of the filter 7.

Next, the exhaust gas temperature integrated value (n
-1) is added to the current exhaust temperature to obtain a new integrated exhaust temperature value.
(n) is obtained (step 102), and a new intake air amount integrated value (n) is obtained by adding the present intake air amount to the intake air amount integrated value (n-1) after the filter regeneration (step 103). The collection counter indicating the collection time after regeneration is incremented (step 104). These exhaust temperature integrated values
(n), the intake air amount integrated value (n), and the collection counter value indicate the integrated value when collection is performed by the filter after regeneration of the filter.

Next, the amount of increase in filter ventilation resistance from the time of filter regeneration is calculated (step 105).
The collection amount DPEMn obtained in step 101 and the collection amount DPEMin obtained at the first time at the start of collection after filter regeneration.
From the difference from it, the ventilation resistance increase amount ΔDPEMn is obtained. Next, the correction coefficient terms X1 to X4 are calculated (step 10).
7). In this case, X1 is calculated by the exhaust gas integrated value (n) ÷ collection counter value, X2 is calculated by the intake air amount integrated value (n) ÷ collection counter value, and X3 is the intake air amount integrated value (n) 増 加 increase in ventilation resistance Quantity Δ
X4 is obtained by the following formula: DPEMn, and X4 is obtained by the following equation.

The correction coefficient term X1 thus obtained
The correction coefficient X is obtained by Expression 1 from 〜X4.

[0021]

X = a + b.X1 + c.X2 + d.X3 + e.X4 where a to d are constants. Then, the collection amount is corrected by multiplying the collection amount DPEMn obtained in step 101 by the correction coefficient X (step 108). FIG. 10 shows the relationship between the corrected trapping amount and the regeneration temperature thus obtained.

Then, the ECU 14 compares the corrected trapping amount with a predetermined set value, and controls the regeneration of the filter 7 when the corrected trapping amount becomes larger than the set value. The above-described integrated value of the exhaust gas temperature, the integrated value of the intake air amount, and the trapping counter value can be cleared to 0 at the start or end of the regeneration control. However, the regeneration is stopped halfway and ends with incomplete regeneration. In such a case, a problem arises in that the relationship between the above-described integrated value and the composition component of the particulates accumulated in the filter is deviated because collection is performed again up to the predetermined collection amount.

Therefore, in order to deal with such a problem,
The ECU 14 performs the integrated value subtraction process shown in FIG. 3 while performing the regeneration control of the filter. First, it is determined whether or not this is the first processing after the start of reproduction (step 20).
1). If it is the first process after the start of the reproduction, the required reproduction time is calculated (step 202). The required regeneration time is calculated from the corrected trapping amount and the secondary air supply amount (the secondary air supply amount supplied from the air pump 9 and is preset in the ECU 14). Next, the integrated value of the exhaust gas temperature, the integrated value of the intake air amount, and the value of the trapping counter are divided by the required regeneration time, and the respective subtracted values of the integrated value of the exhaust gas temperature, the integrated value of the intake air amount, and the collecting counter value are determined (step 20).
3).

In the second and subsequent processes after the start of regeneration, the exhaust gas integrated value, the intake air amount integrated value, and the trap counter value are sequentially reduced by the respective subtraction values (step 2).
04). Therefore, at the time when the regeneration of the filter is completed,
Each integrated value is cleared to zero. However, when the reproduction is stopped halfway, the integrated value at the time of the stop remains, and when collecting the filter, the integration is started from the integrated value at that time.

FIG. 4 shows how one integrated value changes.
Subtraction is performed during the regeneration period based on the integrated value obtained during the collection period. If the filter has been completely regenerated,
As shown by the solid line in the figure, the integrated value is sequentially subtracted and cleared to 0 at the end of the reproduction period. However, when the reproduction is stopped halfway, the integrated value maintains the value at the time when the reproduction was stopped, as shown by the dotted line in the figure, and when the collection is resumed,
The integration is performed from the integrated value.

The processing shown in FIGS. 2 and 3 is repeatedly performed at predetermined intervals (for example, every second). In addition, the result shown in FIG.
7 is a result obtained when the correction coefficient is obtained by eliminating X4 and only X1 is obtained. The result shown in FIG. 7 is obtained when the correction coefficient is obtained by eliminating X1, X3 and X4 and using only X2 in Expression 1. The result shown in FIG. 8 is obtained by eliminating X1, X2, and X4 in Expression 1 and obtaining X3
This is a result obtained when the correction coefficient is obtained only as a correction coefficient. The result shown in FIG.
Is a result obtained when the correction coefficient is obtained with only X4. Therefore, in the above embodiment, X
The correction coefficient may be obtained based on only one of 1 to X4 or a combination with another one.

In addition to the variables described above, the fuel consumption from the start of the collection by the regeneration end filter to the present time, or the start of the collection by the regeneration end filter, other than those described above. It is also possible to add a value obtained by dividing the fuel consumption from the current time to the present by the total intake amount. further,
In the above-described embodiment, the filter 7 is provided in one exhaust passage.
Exhaust particulate purification device provided with
A dual type exhaust particulate purifying device may be provided, in which a filter is provided in each flow path by branching into two flow paths, and the collection and regeneration of particulates are alternately performed by the respective filters by the flow path switching valve. A filter is provided in only one flow path, the other flow path is used as a bypass flow path, and both flow paths are switched by an exhaust switching valve. An exhaust particulate purification device that performs regeneration may be used.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an exhaust particulate purification device showing an embodiment of the present invention.

FIG. 2 is a flowchart showing a trapping amount estimation process by an ECU 14 in FIG. 1;

FIG. 3 is a flowchart showing an integrated value subtraction process by an ECU 14 in FIG. 1;

FIG. 4 is a diagram showing a change state of an integrated value indicating a variable for correcting a trapping amount.

FIG. 5 is a diagram showing a relationship between a trapping amount obtained from a filter differential pressure and a regeneration temperature under various operating conditions.

FIG. 6 is a diagram showing the relationship between the corrected trapping amount and the regeneration temperature when the trapping amount is corrected using the average exhaust temperature with respect to the results shown in FIG.

FIG. 7 is a diagram showing the relationship between the corrected trapping amount and the regeneration temperature when the trapping amount is corrected using the average intake air amount with respect to the result shown in FIG. 5;

FIG. 8 is a diagram showing the relationship between the corrected trapping amount and the regeneration temperature when the trapping amount is modified using the result shown in FIG. 5 by dividing the total intake amount by the ventilation resistance increase amount. .

FIG. 9 is a diagram showing the relationship between the corrected trapping amount and the regeneration temperature when the trapping amount is corrected using the result obtained by dividing the trapping time by the amount of increase in ventilation resistance with respect to the results shown in FIG. .

FIG. 10 is a diagram showing the relationship between the corrected collection amount and the regeneration temperature when the collection amount is corrected using all variables for the results shown in FIG.

[Explanation of symbols]

1 ... Diesel engine, 3 ... Hot wire type flow sensor, 5 ...
Exhaust gas purifier, 7 ... Filter, 8 ... Electric heater, 9 ... Air pump (A / P), 11, 12 ... Pressure sensor, 13 ...
Temperature sensor, 14 ... ECU.

Claims (5)

[Claims] 1. A filter (7) provided in an exhaust passage of a diesel engine (1) for collecting exhaust particulates, and a collection amount estimating means for estimating a collection amount of the exhaust particulates collected by the filter. (101 to 108), wherein the filter is regenerated when the estimated trapped amount reaches a predetermined amount. The exhaust gas temperature detecting device detects the exhaust temperature of the diesel engine. (13), wherein the trapping amount estimating means integrates the exhaust gas temperature detected when the filter is being collected after regeneration of the filter, and calculates the integrated value by the number of times of integration. An exhaust particulate purification device, wherein the trapping amount is corrected based on a divided average value. 2. A filter (7) provided in an exhaust passage of a diesel engine (1) for collecting exhaust particulates, and a trapping quantity estimating means for estimating a trapped quantity of the exhaust particulates collected by the filter. (101-108), wherein the filter is regenerated when the estimated trapped amount reaches a predetermined amount, wherein the intake air amount detection for detecting the intake amount of the diesel engine Means (3), wherein the trapping amount estimating means integrates the intake air amount detected when the filter is being collected after regeneration of the filter, and calculates the integrated value by the number of times of integration. An exhaust particulate purification device, wherein the trapping amount is corrected based on a divided average value. 3. A filter (7) provided in an exhaust passage of a diesel engine (1) for trapping exhaust particulates, and a trapping quantity estimating means for estimating a trapped quantity of the exhaust particulates trapped by the filter. (101-108), wherein the filter is regenerated when the estimated trapped amount reaches a predetermined amount, wherein the intake air amount detection for detecting the intake amount of the diesel engine Means for calculating the amount of increase in filter ventilation resistance from the time of regeneration of the filter; and means for calculating the amount of increase in filter airflow resistance from the time of regeneration of the filter. An exhaust particulate purification device, wherein the trapping amount is corrected based on a value obtained by dividing an integrated value of the intake amount detected at the time of collection by an increase amount of the ventilation resistance. 4. A filter (7) provided in an exhaust passage of a diesel engine (1) for trapping exhaust particulates, and a trapping quantity estimating means for estimating a trapped quantity of the exhaust particulates trapped by the filter. (101-108), wherein the filter is regenerated when the estimated trapped amount reaches a predetermined amount. Means (105) for calculating the amount of increase in the filter airflow resistance from the filter, accumulates the time during which the filter is collecting after regeneration of the filter, and calculates the integrated value as the amount of increase in the airflow resistance An exhaust particle purifying apparatus, wherein the trapping amount is corrected based on a value obtained by dividing the trapped amount. 5. The exhaust particulate cleaning device according to claim 1, further comprising a means (204) for subtracting the integrated value according to a regeneration amount when the filter is regenerated.